The industrial production method of polymethyl methacrylate (PMMA) is conventionally a batch polymerization method using suspension polymerization method. Although this method is a production method suitable for the high-mix low-volume production, since auxiliary agents such as a dispersant are used, these remain in molding materials to thereby reduce the quality. In addition, for the aftertreatment, cleaning with a large volume of water and subsequent drying treatment are needed. Further since the polymerization operation is of a batch type, operations are inefficient and complicated, and simultaneously, the apparatus cost and the operational cost are high. Further in the present situation in which the pollution regulation is becoming strict, the release of a large volume of water or a cleaning water which is used in the polymerization and contains auxiliary agents such as a dispersant and an unreacted monomer is not preferable. The case where a treatment apparatus of the water or the cleaning water is equipped further increases the cost and cannot help bringing about the industrial disadvantage. In order to solve such a problem with the suspension polymerization method, methods for continuously producing methyl methacrylate (MMA) by bulk polymerization are proposed.
Patent Literature 1 discloses a method in which in production of an acrylic resin, by making the amount of a radical polymerization initiator added in a specific range in a continuous tank reactor, and by using a specific condition in a plug flow reactor following the reactor, a methacrylic-based polymer excellent in fabricability is produced in good productivity and stably.